A double-blind, placebo-controlled intravenous immunoglobulin (IVIG) immunotherapy study was performed in 35 infants hospitalized with RSV disease. The treatment was well tolerated, resulted in significant reduction in nasal RSV shedding, and significant improvement in transcutaneous oximetry readings. However, the mean duration of hospitalization was not reduced by IVIG treatment. Followup to date has revealed no harmful effects resulting from immunotherapy of RSV infections. IVIG administered topically offered a significant advantage over systemically administered IVIG, effecting near-complete clearance of pulmonary RSV in cotton rats at a dose 160-fold less than that required for the same therapeutic effect with parenterally administered IVIG. The effect was permanent, and was not due to in vitro viral neutralization during homogenization of pulmonary tissue. Topically administered IVIG, when given prophylactically, provided significant resistance to pulmonary RSV infection for up to seven days, suggesting that there is a specific receptor for IgG in the lungs. A subunit vaccine consisting of F and G glycoproteins of RSV was highly immunogenic, inducing complete resistance to pulmonary RSV infection in cotton rats at a dose as low as 800 picograms of each protein per immunization. At lower doses of F and G, some animals showed peribronchiolar lymphocytic infiltration following RSV challenge, but infiltration of neutrophils was not observed.